I just want to chime in and say that there is not a consistent loss of velocity between semis and bolt guns. AR gas ports are so constricted, and far down the barrel that it is not siphoning off much, if any, velocity.

I would not expect, for example, a 220gr sub in an AR to no longer be subsonic in a bolt action. I would also not expect the same load that I feed my AR10 to suddenly have 100fps more velocity from a bolt action.

Of course, there are other variables (like some barrels are faster than others, and bolt actions being able to withstand higher pressures), but you are not immediately crippling yourself by shooting an AR.

I'm not speaking about subs. I'm talking about full power loads. Have you chronographed AR's and bolt rifles side by side in multiple calibers with the same exact ammo? I pick up about 150 fps with my 110 V-Max ammo from multiple AR's to multiple 16" bolt guns. Why is that? Have you chronographed a 168 or 175 grain in a 308 Win and compared them between an AR and bolt gun? There is a velocity loss going to an AR platform. And that velocity loss on full power ammo is about 75-100 fps with the same barrel lengths. You're not "crippling" yourself with an AR, but you are certainly losing velocity between the two. That's a fact.

Gas port isn't what looses fps in gas gun, it's the opening of the bolt. Same for blowback. That 10k psi at the port can go right back over the bolt into your face. What cartridge was developed for only SA/auto guns?

I mean that also just makes me turn my head a little - I'd be scared if my guns were opening the action while the gun was still pressurized lol.

I've done a lot of fiddling with my AR-10 loads and I can get them to have a bit of ejector smear from the bolt trying to unlock while the case is still pressurized - but I'd be ripping case rims off from the pressure of the case against the chamber walls if it was unlocking at a point where the bullet would lose velocity. I've also never seen any results like that while chronoing and fiddling with my adjustable gas to get it to the point where my gun will cycle.

To Chad's point - I'd be wondering what kind of sloppy chamber and beaver-gnawed rifling my gun had if I was having 150fps swings lmao if the barrels are the same length. That's just an insane amount of difference that I have never, ever, experienced in my loading. To wit, nobody with reloading manuals, factory ammo, Quickload, et al says "This number may vary by up to 150fps depending on whether you're shooting this from a semi auto, so don't even try to gauge how close you are to max pressure by whether your velocity matches up with expected values."

If I can pose a question that can help explain why you think this happens - what do you think will happen if I take my AR-10 with adjustable gas to the range and shoot it both with the gas on and off?

All I have to offer is that a bolt gun uses all the energy of the powder burn to propel the bullet, whereas an AR uses some of the energy to cycle that action. It would seem reasonable to me that the action cycling would cause the AR bullet to have a lower velocity. How much? I have no clue.

Might be worth a try do do what HicksHunter suggested in his last sentence.

How is this for a try . On a couple of wildcat cartridges I developed , I was load testing in an AR before I drilled the gas port . I then drilled after I figured what size hole I needed . Shot again with some of the same ammo . The drilled rifle lost about 50 fps . That is the same rifle , barrel and ammo .

Appreciate the data point.

Think about it. When a round is fired in an AR or semi auto platform, there is a hole (anywhere from 6" to 10"+ inches from the chamber) that gas is re-directed rearward to cycle the action. This is less gas that is no longer propelling the bullet forward once it passes the gas port hole. A bolt gun does not have this hole and doesn't require any energy of the gases to cycle an action. You think that there is no velocity loss between an AR and a bolt gun of the same barrel length, all while knowing this?

I would also not put it past most gas guns to have just a touch 'looser' chamber.

I just think it's actually not a significant factor at all, and is totally outweighed by other factors such as temperature, chamber, and barrel "speed"

So many variations in the rifles will likely make it impossible to come up with a rock solid answer to the question being discussed. But…what I said earlier about diverting AR energy to the cycling of the action will, without a doubt (in my mind) push the bullet a bit slower in the AR. The amount of lost velocity could even be impacted by buffer weight and spring strength. I won’t suggest that the loss in velocity is significant. I don’t have a chrono and I don’t care much about the result, but physics is physics.

I'll try it out next time I go to the range. I've got ARs in 5.56 and .308 with adjustable gas blocks that I'll test out. It'll be a fun experiment for sure.

Is 100 fps significant, no, not really. But there is certainly a velocity loss between the two. If I know I am loading for a gas gun vs a bolt gun, I will load the ammo different for an AR. I will cater the powder and bullet for the AR platform.

Could you give me an example of what powder you'd choose for the AR vs a bolt gun? Bullet I can understand since ARs are mag limited, but a good powder is a good powder is a good powder, right?

I use H335 in my 223 bolt gun and AR, and in my 6.5 Grendel.

50 FPS is realistic but the number was 150 then 100 then 75. I'll buy 50-75. 150 is extreme.

I also use H335 for 5.56X45 in an AR and I have zero use for a bolt gun in 5.56.

For me it makes sense to have an AR/bolt gun pair. I farm hay and have cattle so I have to keep hogs and badgers at bay. An SBR .300blk with thermal is my choice for that.

Since I already have a lot of .300blk ammo on hand, when my kid needed a 100 yard whitetail gun, a bolt action in the same caliber just made sense. Doesn’t kick, it’s fun and has killed everything I have used it on.

As far as other calibers being better, that’s subjective. I have livestock so I don’t want a round with a long range or pass through.

I have a 223 bolt gun. It's more accurate than any AR I've ever run. And way, way more accurate at distance.

I got it because I liked 223 ballistics for where we hunt prairie dogs, and it's cheap/easy/accurate to load for. Took 8 dogs over the weekend with it.

Because my kids were young when I put together the Howa mini for them. I didn't want anything that could be considered high recoil (for a kid). It kills hogs and deer the same amount of deadness at the ranges we hunt. It can do some LR steel banging, not as good as a CM of course but good enough for kids. At the time of purchase, it checked off more boxes than the CM.

Just to put a pin in this I tested out turning off the gas on my AR-10 today. This is a 20" .308 AR-10 w/ rifle-length gas using some light 150gr loads. 44gr W748, 150gr Hornady FMJ, CCI 200 primer, 7.62 NATO mixed headstamp cases. Chronograph is a Magnetospeed V2. Each group was 5 or 6 rounds, depending on how many I grabbed out of my bag.

Rifle:

Normal gas setting:

No gas:

And just for giggles, I turned the gas back on to my normal setting and measured it again.


As predicted, it looks like shutting off the gas doesn't raise the velocity at all. In this case, it actually showed a slight drop, but that's within 1 standard deviation of the average so it's probably just a product of my 5 round tests. I'll leave open the possibility that there could still be a difference with some strange setups (carbine gas on a 20" barrel, for example), or one that has a massive gas port. But I think we're all aware that the majority of a bullet's acceleration has already happened by the time that it passes the gas port, and I'd say this indicates that the sip of gas through the relatively small gas port is not negatively impacting velocities.

"I have a .300 Ham’r AR and a .300 Ham’r bolt gun. The biggest reason is because I wanted to. I don’t feel any other justification is necessary." Adchunts nailed it!!!!!!!

Besides, you guys have not heard my rant on a Gentleman's Rifle. Every gentleman needs a light weight rifle to carry as he walks his plantation. It should have a traditional design and a Walnut stock and blued finish. The chambering needs to be compatible to the game he may encounter during his stroll. A Wilson/Kimber in 300 HAM'R handles the job rather well!

My rambling thoughts on this topic speaking in Generics, and not specifically about you or your rifle:

1) Bolt Rifles are inherently more accurate than AR's.
< Impacted by any number of factors, including tighter tolerance, more rigid mechanical assembly, effects of reciprocating bolt, ease of stabilizing / supporting rifle during shooting, etc.)

2) Shooting a Bolt Rifle is a more intimate, focused experience.
< I am more attuned to a bolt rifle since each shot counts.
< AR tend to shoot quicker with false confidence of a full magazine of follow-up shots.

3) Differences in Velocity.
< There is a loss of gas in the chamber during ignition as gas escapes back around the neck and shoulder of as bullet begins to move out of the case. This is caused by out of spec ammunition and rifle chambers.
< AR ammunition is short at shoulder datum. Manufacturers do this to ensure their ammo will feed and extract from any/all AR's.
< Chambers on most AR's are slightly oversized to ensure mechanical reliability of the firearm... no stuck cases and easy feed/extraction.

4) Barrel Length (apple/orange comparison) generates some velocity noise with most AR's at 16" and Bolt Rifles at 24".

5) Magazine length is usually longer in Bolt Rifle than AR. Ability to load long and fit more powder in Bolt Rifles ammo.

6) Ammunition for Bolt Rifles are loaded to higher pressures. I do load development independently for my Bolt Rifle and AR's, with my ammo for bolt rifles being more stout.

For example 300BO in 16" AR15 vs 18" CZ527 there is on average 150fps difference of which 50fps is barrel length and the remaining +100fps is a hotter charge weight and no loss of pressure in the bolt rifle. The 100fps is not significant. For cases like the 6.5 Grendel there is even more of a increase in velocity.

At the end of the day I grew up shooting bolt actions with peep sights, and it just feels right. If I am only going to take One Shot then my preference is a Bolt Rifle. Style Points!

Since you are going the bolt action route, because you can load higher pressures, and load rounds longer, why get a 300blk bolt rifle? Why not just get a .308? That's my point.

Same here.

Maybe for the quietness when suppressed?